First thing to check are the breather pipes under the engine cover.
My V6 had this problem a while back, and this is what I found on removing the engine cover
And as you can see the T Piece had broken completely at the junction to the top hose
So I bought Part No:
LLH102660
"Hose-camshaft cover to throttle body breather - 12mm - cam cover to throttle"
which cost £13.70 inc VAT from my local Rover dealer (They said the T-Piece on it's own was not available)
And once fitted you can see the improvement
So there you have it, and no more fumes in the cabin :kerstsmiley: